ASPackv102aAlexeySolodovnikov

Hunt Hypothesis

This detection identifies the execution of ASPack v102a packer signatures, which adversaries frequently employ to obfuscate malicious payloads and evade static analysis by standard security tools. Proactively hunting for this behavior in Azure Sentinel is essential to uncover hidden threats that may bypass initial signature-based defenses, allowing analysts to investigate potentially packed executables before they establish persistence or exfiltrate data.

YARA Rule

rule ASPackv102aAlexeySolodovnikov
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 E8 [4] 5D 81 ED 3E D9 43 ?? B8 38 [3] 03 C5 2B 85 0B DE 43 ?? 89 85 17 DE 43 ?? 80 BD 01 DE 43 [2] 75 15 FE 85 01 DE 43 ?? E8 1D [3] E8 79 02 [2] E8 12 03 [2] 8B 85 03 DE 43 ?? 03 85 17 DE 43 ?? 89 44 24 1C 61 FF }

condition:
		$a0 at pe.entry_point
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the ASPackv102aAlexeySolodovnikov detection rule, along with targeted filters and exclusions:

• Scenario: Automated Software Deployment via SCCM/Intune

  • Context: Enterprise deployment tools like Microsoft Endpoint Configuration Manager (SCCM) or Microsoft Intune frequently push application updates that utilize ASPack compression to reduce payload size before installation. The YARA rule may flag the compressed installer executable during the initial download or extraction phase as a potential packed malware.
  • Filter/Exclusion: Create an exclusion for the process path C:\Program Files\Microsoft Configuration Manager\AdminConsole\ and specifically exclude files where the parent process is ccmsetup.exe or intunaprocess.exe. Additionally, filter out alerts where the file hash matches a known “Good” baseline in your threat intelligence feed.

• Scenario: Scheduled Antivirus Definition Updates

  • Context: Major security vendors (e.g., CrowdStrike Falcon, SentinelOne, or Microsoft Defender) often distribute their daily definition updates as ASPack-compressed archives to minimize bandwidth usage. When the update service extracts these definitions, the detection engine may misidentify the extraction utility or the compressed payload itself as a suspicious packed binary.
  • Filter/Exclusion: Exclude processes running under C:\ProgramData\McAfee\ (or equivalent vendor paths) and specifically filter out alerts where the file extension is .cab or .msi located within the vendor’s update directory. Implement a time-based exclusion for these events during known maintenance windows (e.g., 02:00–04:00 UTC).

• Scenario: Internal CI/CD Pipeline Artifact Generation

  • Context: DevOps teams using tools like Jenkins, GitLab Runner, or Azure DevOps often generate build artifacts that